1. Field of the Invention
The present invention relates to beam scanning galvanometers generally, and more specifically, to an arrangement of multiple galvanometers for use in a laser film recording apparatus.
2. Background Art
As one means of recording an image on film, light is selectively introduced to the film in different areas over time, such that the effect of the combined exposures is a composite image. In one known arrangement, a laser beam is focused upon a frame of film. The laser beam is utilized to record a single pixel of an image onto the film. The laser beam is selectively directed at different areas of the frame of film in scan line sequential fashion to generate the composite image. In such an arrangement, beams of red, green and blue light are directed at the frame of film so that a color image is recorded by the film. The process of directing the laser beam at the film must be done with utmost precision or else the resultant image will suffer from visible defects.
In addition, in order for the image to have high resolution, the number of individual pixels or spots on the film which are individually exposed must be very large. The number of individually exposed pixels or spots on a frame of film may be 4000xc3x974000 or more. Thus, in order to expose thousands of frames for a motion picture presentation, the spots are exposed at very high speed, with very high precision spot placement accuracy.
It is known to use a galvanometer to control a reflective surface which is used to deflect a light beam. In such an arrangement, a galvanometer is connected to a mirror and moves the mirror, such as in an oscillating motion. In the case of a laser film recorder, the mirror may be used to deflect the laser beam which exposes the film.
When recording a frame of film, the individual pixels or areas which are exposed by the laser beam are arranged in a Cartesian coordinate system. Pixels are arranged in rows (parallel to an xe2x80x9cxxe2x80x9d-axis) and columns (parallel to a xe2x80x9cyxe2x80x9d-axis). In order to record each pixel, the laser beam and/or film must be moved in both the xe2x80x9cxxe2x80x9d and xe2x80x9cyxe2x80x9d directions.
In prior arrangements, the laser beam is directed over the film in the xe2x80x9cxxe2x80x9d direction using a mirror controlled galvanometer. The film is then moved in the xe2x80x9cyxe2x80x9d direction with respect to the beam. Such arrangements have numerous drawbacks which are well known, including complex film drives and controls.
In order to avoid the shortcomings of systems in which the film is moved, some systems have been devised in which a mirror-controlled galvanometer is used to direct the laser beam in one dimension, and then the entire galvanometer is mounted to a rotary head unit for moving the entire device to direct the beam in the other dimension. Such a system is disclosed in U.S. Pat. No. 5,831,757 having the same inventor and assignee as herein.
This system constitutes an improvement over prior systems. Still, the rate at which the beams may be scanned over the film using this system is limited due to limitations in controlling the movement of the entire device in the required precise manner. When producing a film having thousands of frames, it is desirable to be able to scan the film as quickly as possible.
An improved method and apparatus for deflecting light beams at high frequency for recording film is desired.
The invention is a method and apparatus for deflecting one or more beams using multiple beam scanning galvanometers.
One or more embodiments of the invention comprise a system for deflecting a beam of energy comprising a first reflective surface for directing an incident beam, a first galvanometer coupled to the first reflective surface for rotating the first reflective surface about a first axis, a second reflective surface for directing the incident beam after directed by the first reflective surface, and a second galvanometer coupled to the second reflective surface for rotating the second reflective surface about a second axis, the second galvanometer positioned remotely from the first galvanometer.
In one or more embodiments, the system is a part of a laser film recorder. In such an embodiment, the incident beam comprises combined red, green and blue laser beams. The incident beam is directed by the second reflective surface at a film surface.
One or more embodiments of the invention comprise a method for directing an incident beam, the method comprising the steps of providing a first reflective surface for directing an incident beam, providing a first galvanometer coupled to the first reflective surface for rotating the first reflective surface about a first axis, providing a second reflective surface for directing the incident beam after directed by the first reflective surface, providing a second galvanometer coupled to the second reflective surface for rotating the second reflective surface about a second axis, and locating the second galvanometer remote from the first galvanometer.